Well, there technically is a perimeter in that every corp has (or should have) a firewall between their ISP and the inside of their network which is what I was referring to. I agree with your comment as well because employee's access systems outside the corp net. That access can create an unintended direct link into the system which is where the "thousands of overlapping ones" come in. If your not prepared for the "thousands of overlapping ones" then your not ready for reality.

Bill